This core will provide services that include transformation of lymphocytes, freezing and maintenance of cell lines, preparation of DNA, generation of somatic cell hybrids, and routine cytogenetic assessment of cell lines and lymphocyte cultures, including G-bands and C-bands. Each of these is an essential service required by multiple projects that would have to be duplicated, at considerable cost, in the absence of this core. The core will interact with all four projects and will provide cost savings by centralizing tissue culture activities.